Method and apparatus recuperating boil-off vapor

ABSTRACT

In a fuel vapour recovery system, fuel vapour is drawn off and converted to liquid fuel. The system comprises a compressor ( 34 ), individually closable inlets ( 30, 30   a   , 30   b  . . . ) for the fuel vapour and leading to an inlet duct ( 12 ) of the compressor ( 34 ), a return duct by way of which an outlet of the compressor ( 34 ) communicates with the inlet duct ( 12 ), and a control device ( 66 ) which controls communication between that outlet and the inlet duct ( 12 ) via the return duct in dependence upon the number of the inlets ( 30, 30   a   , 30   b  . . . ) which is open. The system further comprises a tank ( 52 ), a first sensor ( 82 ) which serves to detect when liquid water in the tank ( 52 ) attains a predetermined height in the tank, a second sensor ( 80 ) which serves to detect when liquid fuel in the tank ( 52 ) attains a higher, predetermined height in the tank, a first device ( 58 ) responsive to the first sensor ( 82 ) and serving to cause removal of at least part of the liquid water from the tank when the liquid water attains the first-mentioned predetermined height, and a second device ( 58 ) responsive to the second sensor ( 80 ) and serving to cause removal of at least part of the liquid fuel from the tank ( 52 ) when the liquid fuel attains the higher, predetermined height.

According to a first aspect of the present invention, there is provided a method comprising drawing off fuel undesirably in gaseous form, and converting the fuel in gaseous form to a liquid form.

According to a second aspect of the present invention, there is provided apparatus which draws off fuel undesirably in gaseous form and converts the fuel in gaseous form to a liquid form.

Owing to these two aspects of the invention, the fuel [e.g. petrol, diesel oil, aviation fuel (such as jet Al fuel), or any other fuel that forms VOC (volatile organic compound) gas(es)] in gaseous form (i.e. in the form of a gas, of a vapour, or of a gas/vapour mixture) can be recovered in liquid form. If the method is performed at, for example, a liquid fuel filling site, the fuel recovered in liquid form at the site can be either used in liquid form at the site or transported in liquid form from the site.

According to a third aspect of the present invention, there is provided a method of converting an organic substance in gaseous form to a liquid form, comprising compressing the organic substance in gaseous form.

According to a fourth aspect of the present invention, there is provided an apparatus for converting an organic substance in gaseous form to a liquid form, comprising a compressor which serves to compress the substance in gaseous form.

Owing to these two aspects of the invention, the energy removal necessary to condense the organic substance in gaseous form can be performed at a higher temperature, e.g. at ambient temperature, reducing the amount of cooling which would otherwise be required.

According to a fifth aspect of the present invention, there is provided a method of compressing gaseous matter, comprising opening a plurality of inlets, operating a compressor to draw the gaseous matter through the inlets to an inlet duct of said compressor and to expel said gaseous matter through an outlet of said compressor, closing at least one of said inlets, and operating said compressor to draw the gaseous matter through the open inlet(s) to said inlet duct, to expel the gaseous matter through said outlet and to return at least part of that expelled gaseous matter to upstream of said compressor.

According to a sixth aspect of the present invention, there is provided apparatus for compressing gaseous matter, comprising a compressor, an inlet duct of said compressor, an outlet of said compressor, a plurality of individually closable inlets for the gaseous matter and leading to the inlet duct, a return duct by way of which said outlet communicates with said inlet duct, and a control device which controls communication between said outlet and said inlet duct via said return duct in dependence upon the number of said inlets which is open.

Owing to these two aspects of the invention, it is possible to avoid significantly higher negative pressures arising at (an) open inlet(s) during the times that the other inlet(s) is/are closed compared with the negative pressures at the inlets during the times that all of them are open.

According to a seventh aspect of the present invention, there is provided a method comprising sensing when a heavier fluid attains a predetermined height in a tank, removing at least part of said heavier fluid from said tank when said predetermined height is attained, sensing when a lighter fluid attains a predetermined height in said tank, and removing at least part of said lighter fluid from said tank when the latter predetermined height is attained.

According to an eighth aspect of the present invention, there is provided apparatus comprising a tank, a first sensor which serves to detect when a heavier fluid in said tank attains a predetermined height in said tank, a second sensor which serves to detect when a lighter fluid in said tank attains a predetermined height in said tank, a first device responsive to said first sensor and serving to cause removal of at least part of said heavier fluid from said tank when said heavier fluid attains the first-mentioned predetermined height, and a second device responsive to said second sensor and serving to cause removal of at least part of said lighter fluid from said tank when said lighter fluid attains the second-mentioned predetermined height.

Owing to these two aspects of the invention, it is possible to control the volumes of the heavier and lighter fluids present in the tank.

The heavier and lighter fluids will normally both be liquids and may have an even lighter fluid, which will normally be of gaseous form, above the lighter liquid, with that even lighter fluid being removed from the tank as desired. The fluids can be removed from the tank simply through the opening of valves, if subject to pressure in the tank.

In order that the invention may be clearly and completely disclosed, reference will now be made, by way of example, to the accompanying drawings, in which:—

FIG. 1 is a diagrammatic perspective view of a liquid fuel filling station,

FIG. 2 is a diagram of a vapour recovery system at the station and showing one of a plurality of vapour recovery units of the system,

FIG. 3 is a perspective view, with panels removed for ease of illustration, of that vapour recovery unit of the system,

FIGS. 4 and 5 are underneath, exploded, perspective views of external and internal items of a multi-function tank of the unit, and

FIG. 6 is a diagram of a leak detection arrangement of the unit.

Referring to FIG. 1, the station includes an underground storage tank 2 for liquid petrol 4, but with undesired air/petrol vapour mixture 6 above the petrol 4. A petrol delivery pipe (i.e. pump suction line) 8 extends from the tank 2 to a petrol pump 10 (usually a multi-pump) and a vapour return line 12 extends to a vapour recovery unit 14. At a main ventilation pipe 16 for the tank 2 is another vapour recovery unit 18 virtually identical to the unit 14 and connected to the ventilation pipe 16 by a vapour outlet line 20. The unit 18, which converts petrol vapour from the line 20 into liquid petrol and returns it to the tank 2 via a petrol return line 22 need not be described in further detail. A motor car 24 is shown parked beside the pump 10 having its petrol tank 26 being filled from the pump 10. The vapour return line 12 from a filling nozzle 30 (see FIG. 2) of the pump 10 leads to the unit 14 where the vapour is converted into liquid petrol which is returned via a petrol outlet line 28 to the delivery line 8 (although, if desired, it could instead be returned to the tank 2, such as via an existing return line to the tank 2 conventionally used for returning petrol vapour to the tank 2).

Referring to FIG. 2, the vapour recovery system incorporating the unit 14 will now be described in more detail. During filling, vapour contaminated with some air is sucked from the fill-pipe of the car 24 through the filling nozzle 30 and the line 12 in the form of a hose and a pipe, by means of an oil-free compressor 34. Before entering the compressor 34, the vapour is filtered in a particles filter 36. The inlet and outlet of the compressor 34 are equipped with flame arrestors 38 for safety, and the outlet has a non-return valve 40 to prevent flow reversal. The petrol vapour (and water vapour from moist air) enter(s) an air-cooled heat exchanger 42 where the vapour(s) condense(s) and enter(s) the liquid state(s). During the compression the vapour(s) undergo(es) a small temperature rise. With an ambient temperature of 40° C. the outlet temperature from the compressor 34 could be up to 55° C.

In the heat exchanger 42 energy is released for the petrol and water vapours. A separate motor 44 operates a fan 46 for the heat exchanger 42. The fan 46 automatically stops when the ambient temperature drops to about 5° C.

Condensates and non-condensable gaseous matter, mainly air, flow into a multi-function tank 48 where the water W, denser than the petrol P, accumulates at the bottom, with the petrol P above it and the air A above that. If required, a heater cable 50 is provided to prevent water from freezing in the tank 48 at low temperatures.

A pressure controller 52 in a module 54 containing the multi-function tank 48 keeps the condenser pressure at a constant level.

A float switch 56 senses the levels of water and petrol in the tank 48 and operates solenoid valves 58, to drain off the water W and the petrol P under the action of the internal pressure in the tank 48. The petrol is drained off via a mud- and water-blocking filter 60 through the relevant solenoid valve 58 into the line 28.

Via a high pressure regulator 62 of the controller 52, air and minor amounts of petrol vapour and water vapour pass through to a receiver (an un-illustrated intermediate chamber) and are discharged through a combined bleeder nozzle/flame arrestor 64 to the ambient atmosphere. The water W is discharged to a drain 65.

The system described with reference to FIG. 2 is suited to a multi-pump since it can accommodate more than one filling nozzle 30, e.g. two or more nozzles 30, 30 a, 30 b, etc. In those circumstances, during reduced load, e.g. only one filling nozzle 30 in use, the compressor 34 causes more air to enter the system and the pressure at the bleeder nozzle/flame arrestor 64 increases. At a certain pressure level, a low pressure regulator 66 in the controller 52 opens for air return to the compressor inlet. In this way, an automatic capacity control is achieved and this ensures efficient suction at the filling nozzle.

There would be an insignificant amount of petrol vapour mixed with the air from the bleeder nozzle/flame arrestor 64. This amount could be about 2% to 3% of the total circulation capacity of the system, but the rate of recovered petrol vapour still exceeds all known requirements for petrol vapour recovery at petrol stations.

Referring to FIGS. 4 and 5, the multi-function tank module 54 includes a manifold block 68 to the underside of which is fixed, by way of a fluid-tight sealing ring 70, an open-topped body 72 of the tank 48. Within that tank are the filter 60 mounted, by way of a wing nut 74 and with the interposition of a disc 76, on a pipe 78 leading towards the relevant solenoid valve 58. The float switch 56 has upper and lower floats 80 and 82 for floating on the petrol P and the water W, respectively. An inlet pipe 84 from the heat exchanger 42 is also shown.

Referring to FIG. 6, the unit 14 may contain an automatic leak detection arrangement 86 which stops the compressor 34 when liquid is detected in the inlet line 12. Inserted in the line 12 is a module 88 including an inlet connector 90, an outlet connector 92, a container 94 between the two connectors 90 and 92, a float switch 96 associated with the container 94, and a manual or automatic drain 98 for the container 94. Electrically connected to the float switch 96 is an electronic control device 100 which controls an alarm/failure lamp 102 and a relay 104 controlling the compressor 34.

Petrol vapour and air enter the leak detector through the inlet connector 90 and leave through the outlet connector 92. The float switch 96 floats up and sends an electronic signal whenever a volume above, say, 25-30 ml. accumulates in the container 94. The signal is sent to the device 100 which then illuminates the lamp 102 and actuates the relay 104 to cut off the electrical supply to the compressor 34.

The unit shown in FIG. 3 is constructed as an attachment to almost any existing fuel pump, or to any ventilation pipe from a main fuel tank underground or any fuel tank emitting VOC gas (es). The unit differs from conventional vapour recovery systems because it:

-   -   transforms fuel vapour into liquid fuel (i.e. it does not only         suck off vapour);     -   requires no new piping below the surface or digging in order to         be associated with a fuel pump;     -   interacts with only the start and stop signal from the fuel pump         and therefore not with the flow rate of the pump, thus being         independent of the flow rate;     -   sends liquid fuel directly back into the fuel flow of the pump         (or into existing vapour return piping if necessary).

The unit is usable with any vapour-recovery-equipped filling nozzle and any flexible hose having a vapour return line. It co-operates with one filling nozzle, or with two or more filling nozzles simultaneously, by means of mechanical, step-less adjustment.

The unit is installed alongside the fuel pump, bolted onto the ground. It is connected to the pump through an inlet connection pipe or hose that delivers the mixture of vapour and air into the unit. Furthermore, another connection through a pipe or hose ensures the return of liquid fuel into the suction side of the fuel pumping device of the fuel pump, the pressure side of that device, or return piping for VOC gas(es) if such piping is already present.

If feasible, the unit takes its operating power from the electricity supply of the fuel pump.

The unit is switched on and off with the start and stop signals of the pump, and operates whenever one or more filling nozzles on the pump are in operation. When no nozzles are in operation, the unit is automatically turned off.

The basic function of the unit is to transform fuel vapour into liquid fuel while separating the air (and water) and bleeding off the air. Basically, what takes place during the operation of the unit is that:—

-   1. An uncompressed mixture of fuel vapour and air is sucked into the     unit through the vapour recovery filling nozzle. -   2. The compressor raises the pressure of the mixture to a level     where the fuel vapour components can be condensed with minimal     refrigeration requirements, so that the conversion from vapour to     fuel is particularly cost-effective. -   3. The pressurised vapour/air mixture is fed by the compressor to     the heat exchanger. -   4. The heat exchanger is cooled at the ambient temperature. This     minor decrease in temperature is sufficient to release the amount of     energy from the fuel vapour that is required to transform it into     liquid fuel, but the air remains a gas. -   5. Liquid fuel and air are fed from the heat exchanger to the     multi-function tank. -   6. The combined mud and water filter sees to it that any     dust/mud/other particles or water is separated from the liquid fuel     flow. -   7. Water—if any—is evacuated through the separate water drain. -   8. The tank accumulates liquid fuel and lets the air portion     through. -   9. Liquid fuel without any air or water is sent from the tank to the     fuel outlet. -   10. Pressurised air (containing a small percentage of fuel vapour)     is released via the bleeder nozzle/flame arrestor.

The present system is applicable not only to fuel vapour recovery at fuel stations, but also to various other possibilities of recovery of substances, particularly organic substances, in gaseous form. For example, it could be employed for storage tanks or other vessels containing liquid that forms VOC gas(es). 

1-25. (canceled)
 26. A method comprising drawing off fuel undesirably in gaseous form, and converting the fuel in gaseous form to a liquid form.
 27. A method according to claim 26 and further comprising using in liquid form at a site the fuel converted from the gaseous form at the site.
 28. A method according to claim 26 and further comprising transporting in liquid form from a site the fuel converted from the gaseous form at the site.
 29. A method according to claim 26, wherein said converting comprises compressing said fuel in gaseous form, said compressing comprising opening a plurality of inlets, operating a compressor to draw the fuel in gaseous form through the inlets to an inlet duct of said compressor and to expel said fuel in gaseous form through an outlet of said compressor, closing at least one of said inlets, and operating said compressor to draw the fuel in gaseous form through the open inlet(s) to said inlet duct, to expel the fuel in gaseous form through said outlet and to return at least part of that expelled fuel in gaseous form to upstream of said compressor.
 30. A method according to claim 26, wherein said converting is accompanied by converting water vapour into liquid water, and wherein said liquid water and said fuel in liquid form are fed to a tank, said method further comprising sensing when the liquid water attains a predetermined height in said tank, removing at least part of said liquid water from said tank when said predetermined height is attained, sensing when the fuel in liquid form attains a higher, predetermined height in said tank, and removing at least part of said fuel in liquid form from said tank when the higher, predetermined height is attained.
 31. A method according to claim 30, wherein fuel in gaseous form is present in said tank above the fuel in liquid form, said method further comprising removing from the tank that fuel in gaseous form.
 32. A method according to claim 30, and further comprising subjecting the interior of said tank to pressure, and opening at least one valve to cause at least said fuel in liquid form to flow from said tank under the action of said pressure.
 33. Apparatus which draws off fuel undesirably in gaseous form and converts the fuel in gaseous form to a liquid form.
 34. Apparatus according to claim 33, and comprising a compressor for compressing the fuel in gaseous form, an inlet duct of said compressor, and an outlet of said compressor.
 35. Apparatus according to claim 34 and further comprising a plurality of individually closable inlets for the fuel in gaseous form and leading to the inlet duct, a return duct by way of which said outlet communicates with said inlet duct, and a control device which controls communication between said outlet and said inlet duct via said return duct in dependence upon the number of said inlets which is open.
 36. Apparatus according to claim 33, and further comprising a tank, a first sensor which serves to detect when liquid water in said tank attains a predetermined height in said tank, a second sensor which serves to detect when said fuel in liquid form in said tank attains a higher, predetermined height in said tank, a first device responsive to said first sensor and serving to cause removal of at least part of said liquid water from said tank when said liquid water attains the first-mentioned predetermined height, and a second device responsive to said second sensor and serving to cause removal of at least part of said fuel in liquid form from said tank when said fuel in liquid form attains the higher, predetermined height.
 37. Apparatus according to claim 36, and further comprising a compressor for compressing the fuel in gaseous form, an inlet duct of said compressor, and an outlet of said compressor, said compressor serving to subject the interior of said tank to pressure, and said apparatus further comprising at least one valve openable to allow at least the fuel in liquid form to flow from the tank under the action of said pressure.
 38. A method of converting an organic substance in gaseous form to a liquid form, comprising compressing the organic substance in gaseous form.
 39. A method according to claim 38, wherein said compressing comprises opening a plurality of inlets, operating a compressor to draw the organic substance in gaseous form through the inlets to an inlet duct of said compressor and to expel said organic substance in gaseous form through an outlet of said compressor, closing at least one of said inlets, and operating said compressor to draw the organic substance in gaseous form through the open inlet(s) to said inlet duct, to expel the organic substance in gaseous form through said outlet and to return at least part of that expelled organic substance in gaseous form to upstream of said compressor.
 40. A method according to claim 38, wherein said converting is accompanied by converting a second substance in gaseous form into said second substance in liquid form, and wherein said organic substance in liquid form and said second substance in liquid form are fed to a tank, said method further comprising sensing when the second substance in liquid form attains a predetermined height in said tank, removing at least part of said second substance in liquid form from said tank when said predetermined height is attained, sensing when the organic substance in liquid form attains a higher, predetermined height in said tank, and removing at least part of said organic substance in liquid form from said tank when the latter predetermined height is attained.
 41. A method according to claim 40, wherein organic substance in gaseous form is present in said tank above said organic substance in liquid form, said method further comprising removing from the tank that organic substance in gaseous form.
 42. A method according to claim 40, and further comprising subjecting the interior of said tank to pressure, and opening at least one valve to cause at least said organic substance in liquid form to flow from said tank under the action of said pressure.
 43. An apparatus for converting an organic substance in gaseous form to a liquid form, comprising a compressor which serves to compress the substance in gaseous form.
 44. Apparatus according to claim 43, and further comprising a plurality of individually closable inlets for the organic substance in gaseous form and leading to an inlet duct of said compressor, a return duct by way of which an outlet of said compressor communicates with said inlet duct, and a control device which controls communication between said outlet and said inlet duct via said return duct in dependence upon the number of said inlets which is open.
 45. Apparatus according to claim 43, and further comprising a tank, a first sensor which serves to detect when a second substance in liquid form in said tank attains a predetermined height in said tank, a second sensor which serves to detect when said organic substance in liquid form in said tank attains a higher, predetermined height in said tank, a first device responsive to said first sensor and serving to cause removal of at least part of said second substance in liquid form from said tank when said second substance in liquid form attains the first-mentioned predetermined height, and a second device responsive to said second sensor and serving to cause removal of at least part of said organic substance in liquid form from said tank when said organic substance in liquid form attains the higher, predetermined height.
 46. Apparatus according to claim 45, wherein said compressor serves to subject the interior of said tank to pressure, said apparatus further comprising at least one valve openable to allow at least said organic substance in liquid form to flow from the tank under the action of said pressure.
 47. A method of compressing gaseous matter, comprising opening a plurality of inlets, operating a compressor to draw the gaseous matter through the inlets to an inlet duct of said compressor and to expel said gaseous matter through an outlet of said compressor, closing at least one of said inlets, and operating said compressor to draw the gaseous matter through the open inlet(s) to said inlet duct, to expel the gaseous matter through said outlet and to return at least part of that expelled gaseous matter to upstream of said compressor.
 48. Apparatus for compressing gaseous matter, comprising a compressor, an inlet duct of said compressor, an outlet of said compressor, a plurality of individually closable inlets part of that expelled gaseous matter to upstream of said compressor.
 48. Apparatus for compressing gaseous matter, comprising a compressor, an inlet duct of said compressor, an outlet of said compressor, a plurality of individually closable inlets for the gaseous matter and leading to the inlet duct, a return duct by way of which said outlet communicates with said inlet duct, and a control device which controls communication between said outlet and said inlet duct via said return duct in dependence upon the number of said inlets which is open.
 49. A method comprising sensing when a heavier fluid attains a predetermined height in a tank, removing at least part of said heavier fluid from said tank when said predetermined height is attained, sensing when a lighter fluid attains a predetermined height in said tank, and removing at least part of said lighter fluid from said tank when the latter predetermined height is attained.
 50. Apparatus comprising a tank, a first sensor which serves to detect when a heavier fluid in said tank attains a predetermined height in said tank, a second sensor which serves to detect when a lighter fluid in said tank attains a predetermined height in said tank, a first device responsive to said first sensor and serving to cause removal of at least part of said heavier fluid from said tank when said heavier fluid attains the first-mentioned predetermined height, and a second device responsive to said second sensor and serving to cause removal of at least part of said lighter fluid from said tank when said lighter fluid attains the second-mentioned predetermined height.
 51. A method according to claim 31, and further comprising subjecting the interior of said tank to pressure, and opening at least one valve to cause at least said fuel in liquid form to flow from said tank under the action of said pressure. 